Title: Equipment for Precise Placement of Pesticides on Shade Trees
Abstract: Spraying shade trees for insect and disease control requires thorough coverage of leaf, stem, and trunk surfaces.Much more energy is required than for ground spraying because of the greater distance the spray must be projected and the necessity for covering large surface areas.Tree spraying is normally accomplished with either high-pressure, high-volume hydraulic sprayers or air-carrier sprayers.Hydraulic sprayers use pressure in the liquid system to impart sufficient velocity to the spray droplets to propel them from the point of release to the point of application.Air-carrier sprayers use an airstream to transport and distribute the spray droplets; they may use either high-or low-pressure liquid systems. High-Pressure Hydraulic SprayersHydraulic sprayers used for spraying shade trees generally have tanks, pumps, and control systems that can handle high volumes of spray materials at high pressures.Sprayers are available with tank capacities up to 1500 gallons and with pumps that can supply up to 60 gallons per minute at pressures up to 800 psi.Hand-operated spray guns are used to direct the spray onto the tree.To insure thorough coverage, liquid is applied to the point of runoff.Positive displacement piston pumps are generally used to produce the high pressures required.Abrasion-resistant cylinder linings are desirable to prevent damage to the pump when spraying wettable powders.Piston pumps, however, produce a pulsating flow that can damage gages, valves, hose fittings, and even the pump itself.A surge tank should therefore be installed to absorb the pressure peaks.Air-chamber surge tanks are available for intermittent spraying at pressures up to 400 psi.Although the initial cost of a piston pump is high, its rugged construction, dependability, and long life make it